Small led source with high brightness and high efficiency

ABSTRACT

Small LED sources with high brightness and high efficiency apparatus including the small LED sources and methods of using the small LED sources are disclosed.

This application is a continuation of U.S. application Ser. No.14/528,818 filed on Oct. 30, 2014, which claims the benefit under 35U.S.C. §119(e) of U.S. Provisional Application No. 61/899,723, filed onNov. 4, 2013, each of which is incorporated by reference in itsentirety.

FIELD

The disclosure relates to the field of LED-based illumination productsand more particularly to small LED sources with high brightness and highefficiency and methods for using the small LED sources.

BACKGROUND

The typical footprint of a high-brightness white LED is around 1×1 mm²(such as those used in automotive forward lighting or camera flashapplications); however, white LED sources with a small footprint, highsurface brightness, and high efficiency are desirable for certainapplications such as when they are employed as light sources fordisplays. For example, high brightness enables efficient coupling todisplay waveguides and smaller optics or no optics. Likewise, a smallfootprint helps reduce the size of the optics and the thickness of adisplay system. It is also desirable that the LED's surface be flatrather than dome-shaped, to improve system optical efficiency.

Contemporary literature has discussed how small sources below 300 μm²can be desirable for display applications; however, only monochromaticsources are proposed. White sources require a color-conversion elementfor white-light generation, which makes their miniaturizationchallenging.

Therefore, what is needed is an LED source that has a small surfacearea, and emits a sufficient optical power from substantially onesurface with a sufficient efficiency.

This may be achieved in at least two ways:

-   -   1. Using a low-droop device architecture which can be driven to        a very high current density while maintaining sufficient        efficiency; and    -   2. Designing the electrode scheme such that a large enough        fraction of the footprint is used for light generation.

Embodiments of the disclosure may use either of these approaches, orcombine them. Below are described embodiments following theseapproaches.

SUMMARY

Disclosed herein are methods and devices. One of the disclosed devicescomprises a light-emitting diode having a base area less than 250 μm×250μm; and an emitting surface having an area configured to emitsubstantially white light. The emitting surface is characterized by asurface brightness of 800 mW/mm² or more and at least 80% of the basearea is used for light generation. In certain embodiments, a footprintof about 200 μm×200 μm is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Those skilled in the art will understand that the drawings, describedherein, are for illustration purposes only. The drawings are notintended to limit the scope of the present disclosure.

FIG. 1 shows a tradeoff curve illustrating problems to be addressed whendesigning a small LED source with high brightness and high efficiency.

FIG. 2A is a cross-section view of a wirebond LED for discussingproblems to be addressed when designing a small LED source with highbrightness and high efficiency.

FIG. 2B is a cross-section view of a flip-chip LED for discussingproblems to be addressed when designing a small LED source with highbrightness and high efficiency.

FIG. 3 shows a tradeoff curve of a blue-pumped thin-film design fordepicting performance characteristics to be considered in the design ofa small LED source with high brightness and high efficiency.

FIG. 4 shows a tradeoff curve of a violet-pumped volumetric LED fordepicting performance characteristics to be considered in the design ofa small LED source with high brightness and high efficiency.

FIG. 5 is a tradeoff curve of a violet-pumped volumetric LED design fordepicting how such LEDs maintain a high performance when their footprintis scaled down for designing a small LED source with high brightness andhigh efficiency.

FIG. 6A depicts an LED source placed on a high-reflectivity submount asused in the design of a small LED source with high brightness and highefficiency, according to some embodiments.

FIG. 6B depicts an LED source with a metal-like reflector as used in thedesign of a small LED source with high brightness and high efficiency,according to some embodiments.

FIG. 7 depicts an LED surrounded by a transparent layer as used indesigns for a small LED source with high brightness and high efficiency,according to some embodiments.

FIG. 8 depicts an LED with an undersized color-conversion layer as usedin designs for a small LED source with high brightness and highefficiency, according to some embodiments.

FIG. 9 depicts an LED with an oversized sized color-conversion layer asused in designs for a small LED source with high brightness and highefficiency, according to some embodiments.

FIG. 10A1 and FIG. 10A2 depict an LED surrounded by color-conversionmaterials as used in designs for a small LED source with high brightnessand high efficiency, according to some embodiments.

FIG. 10B through FIG. 10F depict experimental results of devices inaccordance with some of the embodiments disclosed herein.

FIG. 11 depicts an LED with light-blocking regions flanking the LED asused in designs for a small LED source with high brightness and highefficiency, according to some embodiments.

FIG. 12A depicts an LED with color-converting material disposed in acavity of a volumetric LED as used in designs for a small LED sourcewith high brightness and high efficiency, according to some embodiments.

FIG. 12B depicts an LED with wavelength-selective reflector as used indesigns for a small LED source with high brightness and high efficiency,according to some embodiments.

FIGS. 13A-13D depict LED cross-sections during a series of fabricationsteps where an LED is placed on the submount and a dam material isplaced around the small LED source with high brightness and highefficiency, according to fabrication of some embodiments.

FIGS. 14A-14D depict LED cross-sections during a series of fabricationsteps where an LED is placed on the submount and a thin reflector isformed on the sides of the small LED source with high brightness andhigh efficiency, according to fabrication of some embodiments.

FIGS. 15A-15C depict LED cross-sections during a series of fabricationsteps where a color-conversion layer is placed on the top of the smallLED source with high brightness and high efficiency, according tofabrication of some embodiments.

FIGS. 16A-16C depict LED cross-sections during a series of fabricationsteps where a color-conversion material is disposed to surround thesmall LED source with high brightness and high efficiency, according tofabrication of some embodiments.

FIG. 17 depicts an electrode scheme used with an LED having a verticalchip geometry to form a small LED source with high brightness and highefficiency, according to some embodiments.

FIG. 18 depicts an LED having a narrow n-grid that covers part of thetop surface of a small LED source with high brightness and highefficiency, according to some embodiments.

FIG. 19 depicts a flip-chip LED having a narrow n-grid that covers partof the top surface of a small LED source with high brightness and highefficiency, according to some embodiments.

FIGS. 20A1-20I depict examples of uses for the disclosed small LEDsource with high brightness and high efficiency, according to someembodiments.

DETAILED DESCRIPTION

In many applications, it is desirable that an LED source have a surfacebrightness of at least 800 mW/mm². Assuming an operating white-lightwall-plug efficiency of about 20%, such an LED should be driven at apower of about 160 mW and a current density of about 130 A/cm² to emit asufficient amount of light. What is needed is an LED source that has asmall surface area, and emits a sufficient optical power fromsubstantially one surface with a sufficient efficiency.

What follows are definitions, descriptions of materials used in theembodiments, and a detailed discussion of the figures.

The term “exemplary” is used herein to mean serving as an example,instance, or illustration. Any aspect or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects or designs. Rather, use of the wordexemplary is intended to present concepts in a concrete fashion.

The term “or” is intended to mean an inclusive “or” rather than anexclusive “or”. That is, unless specified otherwise, or is clear fromthe context, “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, if X employs A, X employs B, or Xemploys both A and B, then “X employs A or B” is satisfied under any ofthe foregoing instances. In addition, the articles “a” and “an” as usedin this application and the appended claims should generally beconstrued to mean “one or more” unless specified otherwise or is clearfrom the context to be directed to a singular form.

The term “logic” means any combination of software or hardware that isused to implement all or part of the disclosure.

The term “non-transitory computer readable medium” refers to any mediumthat participates in providing instructions to a logic processor.

A “module” includes any mix of any portions of computer memory and anyextent of circuitry including circuitry embodied as a processor.

The term “area” describes the total area of an object and is not tied toa specific shape. For example, and object of dimensions 100×100 μm² andan object of dimensions 10×1000 μm² have the same area, and can becharacterized by “an area of 100×100 μm²”. In other words, an objecthaving dimensions of 100×100 μm² includes an object having an area of10,000 μm². Furthermore, an object having dimensions less than 100×100μm² includes objects in which one of the dimensions is less than 100 μmand objects in which both dimensions are less than 100 μm such as, forexample, 50×100 μm² and 50×50 μm². Also, an object having dimensionsless than 100×100 μm² includes objects having an area less than 10,000μm² such as, for example, 1,000 μm² and 100 μm². Similar definitionsapply to objects having dimensions greater than the indicateddimensions. The areas may be square, rectangular, trapezoidal, circular,oval, or any other suitable shape.

The compositions of phosphors or other wavelength-converting materialsreferred to in the present disclosure comprise any uses of orcombinations of various wavelength-converting materials.

Wavelength conversion materials can be crystalline (single or poly),ceramic or semiconductor particle phosphors, ceramic or semiconductorplate phosphors, organic or inorganic downconverters, upconverters(anti-stokes), nano-particles and other materials which providewavelength conversion. Major classes of downconverter phosphors used insolid-state lighting include garnets doped at least with Ce³⁺;nitridosilicates or oxynitridosilicates doped at least with Ce³⁺;chalcogenides doped at least with Ce³⁺; silicates or fluorosilicatesdoped at least with Eu²⁺; nitridosilicates, oxynitridosilicates orsialons doped at least with Eu²⁺; carbidonitridosilicates orcarbidooxynitridosilicates doped at least with Eu²⁺; aluminates doped atleast with Eu²⁺; phosphates or apatites doped at least with Eu²⁺;chalcogenides doped at least with Eu²⁺; and oxides, oxyfluorides orcomplex fluorides doped at least with Mn⁴⁺. Some specific examples arelisted below:

-   (Ba,Sr,Ca,Mg)₅(PO₄)₃(Cl,F,Br,OH):Eu²⁺, Mn²⁺-   (Ca,Sr,Ba)₃MgSi₂O₈:Eu²⁺, Mn²⁺-   (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu²⁺, Mn²⁺-   (Na,K,Rb,Cs)₂[(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺-   (Mg,Ca,Zr,Ba,Zn) [(Si,Ge,Ti,Zr,Hf,Sn)F₆]:Mn⁴⁺-   (Mg,Ca,Sr,Ba,Zn)₂SiO₄:Eu²⁺-   (Sr,Ca,Ba)(Al,Ga)₂S₄:Eu²⁺-   (Ca,Sr)S:Eu²⁺,Ce³⁺-   (Y,Gd,Tb,La,Sm,Pr,Lu)₃(Sc,Al,Ga)₅O₁₂:Ce³⁺    The group:-   Ca_(1-x)Al_(x-xy)Si_(1-x+xy)N_(2-x-xy)C_(xy):A-   Ca_(1-x-z)Na_(z)M(III)_(x-xy-z) Si_(1-x+xy+z)N_(2-x-xy)C_(xy):A-   M(II)_(1-x-z)M(I)_(z)M(III)_(x-xy-z)Si_(1-x+xy+z)N_(2-x-xy)C_(xy):A-   M(II)_(1-x-z)M(I)_(z)M(III)_(x-xy-z)Si_(1-x+xy+z)N_(2-x-xy-2w/3)C_(xy)    O_(w-v/2)H_(v):A-   M(II)_(1-x-z)M(I)_(z)M(III)_(x-xy-z)Si_(1-x+xy+z)N_(2-x-xy-2w/3-v/3)CxyO_(w)H_(v):A    wherein 0<x<1, 0<y<1, 0≦z<1, 0≦v<1, 0<w<1, x+z<1, x>xy+z, and    0<x−xy−z<1, M(II) is at least one divalent cation, M(I) is at least    one monovalent cation, M(III) is at least one trivalent cation, H is    at least one monovalent anion, and A is a luminescence activator    doped in the crystal structure.-   LaAl(Si_(6-z) Al_(z))(N_(10-z)Oz):Ce³⁺ (wherein z=1)-   (Mg,Ca,Sr,Ma)(Y,Sc,Gd,Tb,La,Lu)₂S₄:Ce³⁺-   (Ba,Sr,Ca)_(x)xSi_(y)N_(z):Eu²⁺ (where 2x+4y=3z)-   (Y,Sc,Lu,Gd)_(2-n)Ca_(n)Si₄N_(6+n)C_(1-n):Ce³⁺, (wherein 0≦n≦0.5)-   (Lu,Ca,Li,Mg,Y) α-SiAlON doped with Eu²⁺ and/or Ce³⁺-   (Ca,Sr,Ba)SiO₂N₂:Eu²⁺,Ce³⁺-   Sr,Ca)AlSiN₃:Eu²⁺-   CaAlSi(ON)₃:Eu²⁺-   (Y,La,Lu)Si₃N₅:Ce³⁺-   (La,Y,Lu)₃Si₆N₁₁:Ce³⁺

For purposes of the application, it is understood that when a phosphorhas two or more dopant ions (i.e. those ions following the colon in theabove phosphors), this is to mean that the phosphor has at least one(but not necessarily all) of those dopant ions within the material. Thatis, as understood by those skilled in the art, this type of notationmeans that the phosphor can include any or all of those specified ionsas dopants in the formulation.

Further, it is to be understood that nanoparticles, quantum dots,semiconductor particles, and other types of materials can be used aswavelength converting materials. The list above is representative andshould not be taken to include all the materials that may be utilizedwithin embodiments described herein.

The limitations found within devices resulting from legacy attemptspresent many opportunities for advancing the state of the art. Forexample, legacy blue-pumped thin-film white LEDs with high brightnesshave been demonstrated. Such 1 mm×1 mm chips at an injection current of1 A have a brightness of about 700 mW/mm² and a wall plug efficiency(WPE) of about 23%. The brightness of these LEDs can be increased bydriving them at higher current densities, however, this reduces thewall-plug efficiency. The reduction in efficiency at high currentdensity is due to several effects, including at least droop in internalquantum efficiency, additional heating, and higher electrical losses athigh current.

What is needed is an LED source that has a small surface area, and emitsa sufficient optical power from substantially one surface with asufficient efficiency. The appended figures and discussion thereto showhow to make and use such LED sources.

FIG. 1 shows a tradeoff curve 100 illustrating problems to be addressedwhen designing a small light emitting diode (LED) source with highbrightness and high efficiency.

FIG. 1 illustrates this tradeoff between efficiency and brightness. InFIG. 1, a state-of-the-art blue-pumped 1 mm² white LED is considered.This is a thin-film LED grown on a sapphire substrate. The LED isinserted into a system with a base temperature of 80° C. (representativeof realistic display systems). The projected performance at variouscurrent densities is shown. At higher current density, brightnessincreases and WPE decreases. It should also be noted that reliablecontinuous operation of such LEDs on sapphire is usually restricted to100 A/cm² and below.

For the device of FIG. 1 operated at 1 A, the brightness and WPEperformance are sufficient for display applications, however, the sourcesize is too large. Upon shrinking the LED to a suitable footprint, theperformance is negatively impacted by several effects, including:

A fixed part of the total LED footprint is used by the n-contacts.

No light generation occurs in this area which is typically 100 μm×100 μmor larger.

When the total LED area is reduced, this inactive area occupies a largerfraction of the total area. Therefore the active area is reduced,leading to worse efficiency droop.

Thermal and electrical resistance scale roughly inversely with the LEDactive area. Therefore, smaller devices have both increased electricalpower losses and higher operating temperatures.

FIG. 2A shows a cross-section view of a wirebond LED 2A00 for discussingproblems to be addressed when designing a small LED source with highbrightness and high efficiency. The LED device shown in FIG. 2A includesLED 203, p-contact 202, submount 208, and wirebond ball 204.

Issues related to the n-contact footprint are illustrated in FIGS. 2Aand 2B. In traditional LEDs (FIG. 2A), the n-electrode occupies aminimum size of about 100 μm² and above. In the case of vertical LEDs,the presence of an n-bond pad (e.g., see wirebond ball 204) that is usedfor wirebonding blocks light emitted from the active region of the LED.If one elects to emit light below the n-pad, a large fraction of thelight is lost; therefore, light generation beneath the n-contact isoften prevented by the introduction of a current-blocking area. Acurrent-blocking area is an area where no current injection occurs(e.g., current-blocking area 203), and therefore no light is generated.This can, for example, be achieved by not forming a p-contact in thatarea—the p-contact may be replaced with an insulating dielectric layer.

FIG. 2B shows a cross-section view of a flip-chip LED 2B00 fordiscussing problems to be addressed when designing a small LED sourcewith high brightness and high efficiency. The LED device shown in FIG.2B includes submount 208, p-contact 202, and n-via 206, and shows across-section of LED devices in which the n-contact area occupies atleast 100 μm².

In the case of flip-chip LEDs current-blocking areas are created by thepresence of large n-vias that contact the n-type material from thebottom of the LED. A potentially large fraction of the p-contact can belost to n-vias.

FIG. 3 shows a tradeoff curve 300 of a blue-pumped thin-film design fordepicting performance characteristics to be considered in the design ofa small LED source with high brightness and high efficiency.

FIG. 3 quantifies the impact that the above issues have on performance.FIG. 3 shows several LED footprints (e.g., 1 mm×1 mm 302, 150 μm×150 μm304, 200 μm×200 μm 306, etc.). When the footprint is reduced from 1 mm×1mm to 200 μm×200 μm and 150 μm×150 μm, performance is significantlyreduced.

These issues and limitations are fundamental: as the footprint of aGaN-based LED becomes smaller, the loss of relative active areaincreases droop, and the electrical and thermal resistance alsoincrease. This increased electrical and thermal resistance leads to areduction in performance. What is needed is an LED source, which has asmall surface area, and emits a sufficient optical power fromsubstantially one surface with a sufficient efficiency. This may beachieved in various ways. As examples:

-   -   1. Using a low-droop device architecture that can be driven to a        very high current density while maintaining sufficient        efficiency.    -   2. Designing the electrode scheme such that a large enough        fraction of the footprint is used for light generation (e.g.,        light is not prevented from escaping by the presence and        juxtaposition of the electrode).

Embodiments of the disclosure may use either of these approaches, orcombine them. Below are described embodiments following theseapproaches.

The low-droop approach employs LEDs with reduced efficiency loss at highcurrent density. This is possible, according to some embodiments,through the use of violet-pump LEDs on a bulk III-nitride substrate.These LEDs may be grown on a polar, non-polar, or semi-polar plane, andmay have any shape (e.g., having a base that is square, rectangular,polygonal or rectilinear, or circular or oblong, etc.).

FIG. 4 shows a tradeoff curve 400 of a violet-pumped volumetric LED fordepicting performance characteristics to be considered in the design ofa small LED source with high brightness and high efficiency. The numberson the graph indicated the corresponding current density (A/cm²).

FIG. 4 shows the performance of a violet-pumped volumetric white LED 404grown on a bulk GaN substrate, with a footprint of 250 μm×250 μm. The 1mm² blue-pumped thin film white LED 402 device of FIG. 1 is also shownfor comparison. At a current density of 50 A/cm², the two devices havesimilar performance. However, at higher current density, theviolet-pumped white LED maintains higher performance over a wide rangeof current density operation. This is due to its lower efficiency droop,and also to its lower electrical resistance, which is attributable atleast in-part to the use of a bulk GaN substrate.

FIG. 5 shows a tradeoff curve 500 of a violet-pumped white volumetricLED design for depicting how such LEDs maintain a high performance whenthe footprint is scaled down for producing a small LED source with highbrightness and high efficiency.

FIG. 5 shows how such LEDs maintain a high performance when theirfootprint is scaled down. As shown, performance is only marginallyaffected over the range, due at least in part to the low droop and lowelectrical resistance of the devices. In addition, operation at highcurrent density (200 A/cm² and greater) is reliable. Due to the presenceof the bulk substrate, such LEDs are usually thick (100 μm to 200 μm)and emit light from all sides. In some cases, however, the LED may bethinner, for example, 50 μm thick or 10 μm thick, or thinner. In certainapplications, (e.g., for display applications), it is preferred to useLEDs in a configuration such that white light is emitted only from orsubstantially from one surface.

The performance of many LED configurations are shown in FIG. 5, inparticular corresponding to a footprint are of 250 μm×250 μm 502, 200μm×200 μm 504, 150 μm×150 μm 506.

Embodiments of the invention are not limited to these footprints. Forexample, in some embodiments, the footprint is 10 μm×10 μm or 1 μm×1 μm.

FIG. 6A depicts an LED source 6A00 placed on a high-reflectivitysubmount as used in the design of a small LED source with highbrightness and high efficiency.

As shown in the embodiment of FIG. 6A, the LED source is placed on ahigh-reflectivity submount 208. The top surface dimensions are 150μm×150 μm. The sidewalls of the LED are covered by a reflective material604. The top surface of the LED 606 is covered by a color-conversionmaterial 602 such as a phosphor, with surface dimensions similar to thatof the LED. Light is substantially emitted by the top surface of thecolor-conversion material. The sidewall reflective material 604 may be adiffuse reflector, such as a TiO₂-based reflector, a metallic mirror, adichroic mirror, or a combination of these elements. In certainembodiments, the reflective material and/or the submount comprises adiffuse reflector, a metal material, a dielectric stack, or acombination of any of the foregoing.

In some embodiments, the use of a high-reflectivity submount can beadvantageous to reduce optical loss and thus improve opticalperformance. In some cases, the reflectivity is high at the emissionwavelength of the pump LED. In some cases, the reflectivity is high in alarge range of angles and wavelengths (e.g. across the visible range) toreduce optical loss for converted light. In some embodiments, forexample, reflectivity is higher than 80% (or higher than 90%, or higherthan 95%) across the visible range and at all incident angles of light.

FIG. 6B depicts an LED source 6B00 with a metal-like reflector as usedin the design of a small LED source with high brightness and highefficiency.

In the embodiment of FIG. 6B, the LED source is covered on its sideswith a first reflective material (e.g., reflective material 604) that isplanar to the top of the LED. A second reflector 607, such as a metalreflector, with a small aperture filled with the color-conversionmaterial 602 is then placed on top of the LED. The second reflectorserves as a light blocking material and cavity for the color-conversionmaterial.

FIG. 7 depicts an LED 700 surrounded by a transparent layer as used indesigns for a small LED source with high brightness and high efficiency.

In such embodiments as depicted in FIG. 7, the LED is surrounded by atransparent material 609 (e.g., as air or silicone). In one suchembodiment, the transparent material 609 is located all around the LED.In another embodiment, the transparent material is located only on thesides of the LED. In another embodiment, the transparent material islocated only on top of the LED. The embodiment further comprises areflective material 604 in proximity to the LED and/or in proximity tothe color conversion material. In some embodiments, an aperture isformed in the reflective material where the color conversion material islocated.

FIG. 8 depicts an LED 800 with an undersized color-conversion layer asused in designs for a small LED source with high brightness and highefficiency. The LED device shown in FIG. 8 includes LED 606, submount208, reflective material 604, and undersized color-conversion material602.

The use of such an undersized color-conversion layer may be advantageousto further reduce the optical size of the white light-emitting surfacewith respect to the surface of the pump LED, thus increasing thebrightness of the system.

FIG. 9 depicts an LED 900 with an oversized sized color-conversion layeras used in designs for a small LED source with high brightness and highefficiency. The LED device shown in FIG. 9 includes LED 606, submount208, reflective material 604, and oversized color-conversion material602.

The use of such an oversized color-conversion layer may be advantageousto improve the conversion efficiency of the system, by limiting thedeleterious backscattering of light in the LED die.

FIG. 10A1 depicts an LED 10A100 surrounded by color-conversion materialas used in designs for a small LED source with high brightness and highefficiency. The LED device shown in FIG. 10A1 includes LED 606, submount208, reflective material 604 and color-conversion material 602.

In this embodiment, the color-conversion material is placed in proximityto the LED and reflective material is placed in proximity to the sidesof the color-conversion material. This configuration may be advantageousto improve the optical efficiency of the system, by limiting thedeleterious backscattering of light in the LED die. Further, in thisconfiguration the light backscattered to the siders of the LED is moresubstantially color-converted light (and less substantially direct pumplight from the LED). Such longer-wavelength converted light incurs loweroptical loss when backscattered in the die, thus improving opticalefficiency.

FIG. 10A2 depicts an LED 10A200 surrounded by color-conversion materialas used in designs for a small LED source with high brightness and highefficiency. The LED device shown in FIG. 10A2 includes LED 606, submount208, reflective material 604, color-conversion material 602, and air gap10A210.

The embodiment shown in FIG. 10A2 is similar in some aspects to that ofFIG. 10A1, however, an air gap 10A210 is present in-between the colorconversion material and the reflective material. The purpose of the airgap is to reduce the amount of light escaping the color conversionmaterial and reaching the reflective material due to total internalreflection (TIR) at the air gap interface. This can further improvedevice performance as light undergoing TIR is reflected without anyloss. In some embodiments, the air gap has a width of 1 μm, 10 μm, 100μm. In other embodiments, the gap is formed by a low-index substanceother than air. For example, the color-conversion material may be formedof phosphor particles in an encapsulant with index n approximately equalto 1.4 or 1.5, and the low-index substance has an index approximatelyequal to 1.2 or 1.3. The low index may be obtained by a variety ofmeans, for example by dielectric materials or by pores such as airpores.

In addition to the selection of color-conversion materials (e.g., asheretofore described) the selection of materials with high reflectivitycan be made in order to reduce the source size while maintaining a highefficiency. The following section presents experimental dataillustrating this.

FIG. 10B shows the measured optical reflectivity spectrum of twodifferent diffuse reflectors at normal incidence from air. The lowerreflectivity material (reflector 2) has a reflectivity of less than 94%for wavelengths >500 nm. The higher reflectivity material (reflector 1)has a reflectivity of >97% for wavelengths >500 nm. Such materials canbe used in embodiments. In some embodiments the reflectance is onlyslightly wavelength dependent. For example, in some embodiments, thereflectance can have a constant value within 1% or within 5% in therange from 400 nm to 700 nm. In some embodiments, the reflectance has aconstant value within 1% or within 5% in the range from 450 nm to 700nm. In some embodiments the reflectivity is higher than a given value(for example 90% or 95% or 99%) at all angles of incidence from theincoming medium (which may be air or an encapsulant).

The reflectivity of a high reflectivity material can be 96%, 97%, 98%,99% or 100% depending on the material composition and method ofconstruction. These can pertain to the values coming from air, or froman encapsulating medium (such as a silicone). In some embodiments, whitediffuse reflector materials can be made from titanium oxide particles(rutile, anatase or brookite phase) dispersed in a matrix of silicone orepoxy. The titanium oxide particle sizes may range from 50 nm orsmaller, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm to 600 nm. In otherembodiments, the diffused white reflector can be composed of a networkof polyethylene or polytetrafluoroethylene particles or fibers withinter-penetrating air pores or gaps. In some embodiments, the diffusewhite reflector comprises a material with air pores such as hollowsilica spheres embedded in an encapsulant. In some embodiments, dichroicspecular reflectors can be constructed from alternating layers ofdielectric material, which layers have different refractive indices. Insome embodiments, metallic specular reflectors can be made from smoothfilm of silver metal that is more than 200 nm in thickness.

FIG. 10C shows the measured white wall plug efficiency (WPE) of LEDmodules (CCT of 3000K, CRI of 80, current of 80 mA and junctiontemperature of 85° C.) with circular light emitting areas of varyingradii. The configuration of the LED modules is shown in FIG. 10A. Insome embodiments, the radius of the light-emitting region can be 3 mm, 2mm, 1 mm, 0.5 mm, 0.25 mm, 0.1 mm or smaller. As the radii of theemitting region is reduced from 2 mm to 0.35 mm, the wall plugefficiency decreases monotonically due an increase of optical losses inthe white reflector cup surrounding the light-emitting region. Thecurves compare devices built with a higher reflectivity cup (Reflector1) and devices built with a lower reflectivity cup (Reflector 2) asshown in FIG. 10B. For large radii (>1 mm), the effect of thereflectivity of the cup is less pronounced, the WPE difference betweenReflector 1 and Reflector 2 may be less than two percent. For smallradii (<0.5 mm), the reflectivity of the reflector material has a largeeffect on the WPE of the device, which could differ by more than fivepercent.

FIG. 10C illustrates results of using of materials with highreflectivity (e.g., to maintain performance when the reflector becomesclose to the LED emitter). Some embodiments are further reduced infootprint, and the use of high-reflectivity materials becomes moredominant in such designs.

FIG. 10D shows the surface brightness (in W/mm²) of LED modules (CCT of3000K, CRI of 80, current of 80 mA and junction temperature of 85° C.)with circular light emitting areas of varying radii. As the emittingarea of the LED is decreased from a circular source with 2 mm radius toone with 0.35 mm radius, the surface brightness increases monotonicallybecause the total light emitted from the source is confined to a smallerarea. The curves compare devices built with a higher reflectivity cup(Reflector 1) and devices built with a lower reflectivity cup (Reflector2) as shown on FIG. 10B. The surface brightness of LEDs packaged withReflector 1 increase more with decreasing emitting area compared to LEDspackaged with Reflector 2, which is composed of a lower reflectivitymaterial. For a circular source radius of 0.35 mm, LEDs made withreflector 1 exhibit 50% greater surface brightness due to lower opticallosses to the reflector cup.

In some applications that require high surface brightness whilemaintaining reasonable white wall plug efficiency, the reflectivity ofthe cup material can be selected, managed or optimized. Given the sameinput current of 80 mA, the surface brightness of the source can beincreased by confining the light emitting area to a smaller region, asshown in FIG. 10D. However, this comes at the cost of decreasing whiteWPE (as shown in FIG. 10E) due to an increase of optical losses to thereflective cup. For LEDs assembled with a lower reflectivity material(see Reflector 2), the achievable surface brightness is severely limitedbecause the efficiency of the source drops sharply as the light-emittingarea is reduced. For LEDs assembled with a higher reflectivity material(see Reflector 1), high surface brightness can be achieved with a muchlower penalty in white WPE. In the example shown in FIG. 10E, thesurface brightness of LEDs assembled with Reflector 1 can be increasedby more than 10 times while incurring no more than 15% loss in whiteWPE.

FIG. 10F depicts WPE as a function of the height of the cup. In additionto the aforementioned variables, the height of the cup can alsodramatically impact the overall white WPE of small LED sources with lessthan 1 mm² of emitting area. In some embodiments, the thickness of thereflective cup can be 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm or 0.1 mm.As shown in FIG. 10F, for an LED device (CCT of 3000K, CRI of 80,operating at 80 mA and junction temperature of 85° C.) with a 0.5 mmradius circular light-emitting area, the white WPE of the sourceincreases as the thickness of the reflective cup is reduced (thephosphor blend is tuned to maintain the same color point in each case).Given the same emission area, when the white LED thickness (determinedby the cup height) is reduced, the proportion of light that impingesupon the reflective cup also decreases, resulting in less optical loss.For example, FIG. 10F shows that when the height of the cup (Reflector2) is reduced from 0.5 mm to 0.25 mm, the white WPE is increased by morethan 15%. This directly translates into 15% higher surface brightnessbecause the emitting area is maintained.

In certain embodiments a combined thickness of the submount, the atleast one LED, and the light-converting material is less than 2 mm, lessthan 1 mm, and in certain embodiments, less than 0.5 mm.

Other measures can be taken to reduce the loss in the reflectivematerial surrounding the LED. In some cases, an air gap is createdbetween the LED and the reflective material, or between the colorconversion material and the reflective material. In such embodiments,the probability for light to reach the reflective material is decreased.For example, if the color conversion material surrounding the die has anindex of about 1.4, only 50% of the diffuse light in the colorconversion material will escape to the air gap and require reflection bythe reflective material. The air gap may, for example, have a thicknessof about 1 μm, 10 μm, 100 μm. FIG. 10A2 illustrates these embodiments.

Just as is the case for the reflective material, the reflectivity of thesubmount is important to maintain performance. In some embodiments,light bounces multiple times on the submount before it escapes, so thatthe one-bounce loss from the submount is amplified. Therefore, ahigh-reflectivity submount is desirable. Such high-reflectivity mirrorscan be composed of a metallic mirror (such as silver) coated by adielectric layer, or a series of dielectric layers acting as a dichroic.In some embodiments, a low-index layer is present in the stack of thesubmount to obtain a total internal reflection (TIR) effect: large-anglelight undergoing TIR is perfectly reflected and does not travel to lossylayers of the submount.

FIG. 11 depicts an LED 1100 with light-blocking regions flanking the LEDas used in designs for a small LED source with high brightness and highefficiency. The LED device shown in FIG. 11 includes LED 606, submount208, reflective material 604, color-conversion material 602, andlight-blocking material 1102.

In this embodiment, a light-blocking material 1102 is placed above theactive region of the LED 606 to prevent emission of light that maydiffuse through the reflective material 604. This light-blockingmaterial 1102 may, for example, be a metal, or a substantially-blackmaterial.

The sidewalls of the LED need not be vertical. In some embodiments, thesidewalls of an LED can be slanted with either a positive or a negativeangle from the vertical.

In some embodiments, the LED is thinned down so that only a smallfraction of the light can escape from the sides. For example, thevertical-to-horizontal aspect ratio of the LED can be less than 10%. Insome of these embodiments, no sidewall reflector is used. In someembodiments, this thinning approach is combined with a sidewallreflector such as one of the reflectors described in previousembodiments.

FIG. 12A depicts an LED 12A00 with color-converting material disposed ina cavity of a volumetric LED as used in designs for a small LED sourcewith high brightness and high efficiency. The LED device shown in FIG.12A includes LED 606, submount 208, reflective material 604,color-conversion material 602, and light-blocking material 1102.

In the embodiments of FIG. 12A, the volumetric nature of the LED die canbe used. A cavity is etched in the LED—for example, in the bulk GaNsubstrate. The cavity can be etched by dry etching or by chemicaletching. This cavity is then filled with a white-emittingcolor-conversion material. This enables a thin LED device profile. Thesidewalls of the LED may be coated with a reflective material, and alight-blocking material may be used to mask the bare outer edge of theLED.

FIG. 12B depicts an LED 12B00 with wavelength-selective reflector 1204as used in designs for a small LED source with high brightness and highefficiency. The LED device shown in FIG. 12B includes LED 606, submount208, color-conversion material 602, reflective material 604, dam 12B02,wavelength-selective reflector 1204 and metal cap 1206.

In certain embodiments of FIG. 12B, a wavelength-selective reflector1204 such as a dichroic mirror is incorporated to the design. Thismirror may reflect the direct emission from the LED but transmit theconverted light, thus decreasing or removing the need for acolor-conversion material layer on top of the LED chip. Some embodimentsinclude a metal cap 1206 that creates an aperture through which thedirect emissions from the LED can pass. This metal cap can be used toshrink the emitting area, for applications requiring a specific smallemitting area.

Further, some embodiments include a dam element 12B02. The dam can beused in some fabrication flows, for example: first the dam is placedaround the LED, and then the color-conversion material is dispensed(i.e. in liquid of paste form) in the dam around the LED, and cured toreach a solid phase.

FIGS. 13A-13D depict LED cross-sections during a series of fabricationsteps (e.g., see cross-section 13A00, see cross-section 13B00, seecross-section 13C00, see cross-section 13D00) where an LED is placed onthe submount and a dam material is placed around the small LED sourcewith high brightness and high efficiency. The devices shown in FIGS.13A-13D include LED 606, submount 208, dam 12B02, reflective material604, color-conversion material 602, and light-blocking material 1102.

In such a technique, the LED is placed on the submount and a dam element12B02 is placed around the LED. Part of the volume between the dam andthe LED is filled with a reflective material 604. Part of the volumearound the LED is filled with color-conversion material 602. Alight-blocking layer 1102 is formed above.

FIGS. 14A-14D depict LED cross-sections during a series of fabricationsteps (e.g., see cross-section 14A00, see cross-section 14B00, seecross-section 14C00, see cross-section 14D00) where an LED is placed onthe submount and a thin reflector is formed on the sides of the smallLED source with high brightness and high efficiency. The devices shownin FIGS. 14A-14D include LED 606, submount 208, reflective material 604,and color-conversion material 602.

As depicted in FIGS. 14A-14D, the LED is placed on the submount 208 anda thin reflector 604 (such as a metal) is formed on the sides of theLED. The color-conversion material 602 is the placed on top of the LED.In some cases (e.g., as shown in FIGS. 14B-14D) a thin reflector coversboth the sides of the die and color-conversion-material mesa tofacilitate top-side only emissions.

FIGS. 15A-15C depict LED cross-sections during a series of fabricationsteps (e.g., see cross-section 15A00, see cross-section 15B00, seecross-section 15C00, see cross-section 15D00) where a color-conversionlayer is placed on the top of the small LED source with high brightnessand high efficiency. The LED devices shown in FIGS. 15A-15C include LED606, color-conversion material 602, tape 1502, submount 208, andreflective material 604.

In another technique, the color-conversion layer is first placed on thetop of the LED—for example while the LED is on a tape. The LED is thenattached to the submount. Finally the reflective material is formedaround the LED.

FIGS. 16A-16C depict LED cross-sections during a series of fabricationsteps 16A00-16C00 where a color-conversion material is disposed tosurround the small LED source with high brightness and high efficiency.The LED devices shown in FIGS. 16A-16C include LED 606, color-conversionmaterial 602, tape 1502, submount 208, and reflective material 604.

In another technique, the color-conversion layer is first placed aroundLED (e.g., while the LED is on a tape). The LED is then attached to thesubmount. The reflective material is formed around the color-conversionmaterial.

Some approaches use a modified electrode layout to enable highbrightness operation from a small footprint. As previously discussed andshown as pertaining FIG. 2, in traditional LEDs, the n-electrodeoccupies a minimum size of 100 μm×100 μm and above. For a devicefootprint of 200 μm×200 μm, only 75% of the device area is being usedfor light generation. In some embodiments of the present disclosure, thedevice area is 200 μm×200 μm or less, and the light-generating area isat least 80% of the device area.

In some embodiments, this is obtained using a vertical chip geometry.

FIG. 17 depicts an electrode scheme used with an LED 1700 having avertical chip geometry to form a small LED source with high brightnessand high efficiency.

As shown in FIG. 17, a narrow n-grid 1703 (for example, 5 μm wide or 1μm wide) covers part of the top surface of the LED. The electrode runsto the side of the LED along one of the sidewalls 1704 that has beenpassivated, for example, by deposition of a dielectric layer (seepassivated sidewall 1704). An n-wirebond ball 204 is placed away fromthe LED so that it does not contribute to light occlusion or shadowingor a reduction of the light generation area. The narrow n-grid has anarea that is less than 20% of the footprint of the LED. Also shown inFIG. 17 is a cross-section 1750 of the LED, showing the p-contact 1705(where light is generated) and a current-blocking area 1706 under then-contact 1702 to prevent light generation there.

FIG. 18 depicts an LED 1800 having a narrow n-grid that covers part ofthe top surface of a small LED source with high brightness and highefficiency.

In another embodiment, as shown in FIG. 18, the n-grid runs to the sideof the LED on a planarizing layer 1802 rather than on a sidewall of theLED.

In some embodiments, the modified electrode layout is obtained in aflip-chip technology.

FIG. 19 depicts a flip-chip LED 1900 having a narrow n-grid that coverspart of the top surface of a small LED source with high brightness andhigh efficiency. The device shown in FIG. 19 includes p-contact 202,n-contact 1702, and dielectric 1902.

In one such embodiment (as shown in FIG. 19), the n-contact area is asmall fraction of the light-emitting area. The submount contains severallayers which reconfigure the n and p electrodes, increasing the area ofthe n-electrode under the LED for interconnect purposes. Dielectriclayers (e.g., dielectric 1902) are employed to isolate the p and nelectrodes. The two p-contact parts of the LED are connected laterallyout of the plane of the figure.

As shown in FIGS. 17 and 18, the n-electrode may have a cross shape oranother shape in order to improve current spreading in the LED.

Any of the schemes shown or referenced in FIGS. 18 and 19 use the samearea of n-contact and light-generation blocking layers near the activelayer, however, flip-chip embodiments often features a guard band aroundthe n-contact that operate to decrease the usable area for lightemission. On the other hand, the flip-chip configuration ismore-compatible with certain fabrication techniques, which can be usedto create small emitting surfaces.

The examples herein describe in detail examples of constituent elementsof the herein-disclosed embodiments. It will be apparent to thoseskilled in the art that many modifications, both to materials andmethods, may be practiced without departing from the scope of thedisclosure.

Embodiments of the herein-disclosed LEDs can be used in various lampsand in various applications. Such lamps and applications can includeautomotive forward lighting or camera flash applications. Theaforementioned automotive forward lighting or camera flash applicationsare merely some embodiments. Other lamps can include lamps that conformto fit with any one or more of a set of mechanical and electricalstandards. Table 1 gives standards (see “Designation”) and correspondingcharacteristics.

TABLE 1 Desig- Base Diameter IEC 60061-1 nation (Crest of thread) Namestandard sheet E5  5 mm Lilliput Edison Screw 7004-25 (LES) E10 10 mmMiniature Edison Screw 7004-22 (MES) E11 11 mm Mini-Candelabra Edison(7004-6-1) Screw (mini-can) E12 12 mm Candelabra Edison Screw 7004-28(CES) E14 14 mm Small Edison Screw (SES) 7004-23 E17 17 mm IntermediateEdison 7004-26 Screw (IES) E26 26 mm [Medium] (one-inch) 7004-21A-2Edison Screw (ES or MES) E27 27 mm [Medium] Edison Screw 7004-21 (ES)E29 29 mm [Admedium] Edison Screw (ES) E39 39 mm Single-contact (Mogul)7004-24-A1 Giant Edison Screw (GES) E40 40 mm (Mogul) Giant Edison7004-24 Screw (GES)

Additionally, the base member of a lamp can be of any form factorconfigured to support electrical connections, which electricalconnections can conform to any of a set of types or standards. Forexample, Table 2 gives standards (see “Type”) and correspondingcharacteristics, including mechanical spacing between a first pin (e.g.,a power pin) and a second pin (e.g., a ground pin).

TABLE 2 Pin center Pin Type Standard to center diameter Usage G4 IEC60061-1 4.0 mm 0.65-0.75 mm MR11 and (7004-72) other small halogens of5/10/20 watt and 6/12 volt GU4 IEC 60061-1 4.0 mm 0.95-1.05 mm(7004-108) GY4 IEC 60061-1 4.0 mm 0.65-0.75 mm (7004-72A) GZ4 IEC60061-1 4.0 mm 0.95-1.05 mm (7004-64) G5 IEC 60061-1 5 mm T4 and T5(7004-52-5) fluores- cent tubes G5.3 IEC 60061-1 5.33 mm 1.47-1.65 mm(7004-73) G5.3-4.8 IEC 60061-1 (7004-126-1) GU5.3 IEC 60061-1 5.33 mm1.45-1.6 mm (7004-109) GX5.3 IEC 60061-1 5.33 mm 1.45-1.6 mm MR16 and(7004-73A) other small halogens of 20/35/50 watt and 12/24 volt GY5.3IEC 60061-1 5.33 mm (7004-73B) G6.35 IEC 60061-1 6.35 mm 0.95-1.05 mm(7004-59) GX6.35 IEC 60061-1 6.35 mm 0.95-1.05 mm (7004-59) GY6.35 IEC60061-1 6.35 mm 1.2-1.3 mm Halogen (7004-59) 100 W 120 V GZ6.35 IEC60061-1 6.35 mm 0.95-1.05 mm (7004-59A) G8 8.0 mm Halogen 100 W 120 VGY8.6 8.6 mm Halogen 100 W 120 V G9 IEC 60061-1 9.0 mm Halogen(7004-129) 120 V (US)/ 230 V(EU) G9.5 9.5 mm 3.10-3.25 mm Common fortheatre use, several variants GU10 10 mm Twist-lock 120/230- volt MR16halogen lighting of 35/50 watt, since mid- 2000s G12 12.0 mm 2.35 mmUsed in theatre and single-end metal halide lamps G13 12.7 mm T8 and T12fluorescent tubes G23 23 mm 2 mm GU24 24 mm Twist-lock for self-ballasted compact fluores- cents, since 2000s G38 38 mm Mostly used forhigh- wattage theatre lamps GX53 53 mm Twist-lock for puck- shapedunder- cabinet compact fluores- cents, since 2000s

The list in Table 2 is representative and should not be taken to includeall the standards or form factors that may be utilized withinembodiments described herein.

In some embodiments the present disclosure can be applied towarddirectional lighting applications as depicted in FIG. 20A1 through FIG.20I. In these embodiments, one or more light-emitting diodes 20A10, astaught by this disclosure, can be mounted on a submount or package toprovide an electrical interconnection. The submount or package can be aceramic, oxide, nitride, semiconductor, metal, or combination thereof,that include electrical interconnection capability 20A20 for the variousLEDs. The submount or package can be mounted to a heatsink member 20B50via a thermal interface. The LEDs can be configured to produce a desiredemission spectrum, either by mixing primary emission from various LEDs,or by having the LEDs photo-excite wavelength down-conversion materialssuch as phosphors, semiconductors, or semiconductor nanoparticles(“quantum dots”), or a combination of any of the foregoing. The totallight emitting surface (LES) of the LEDs and any down-conversionmaterials can form a light source 20A30. One or more light sources canbe interconnected into an array 20B20, which is in turn in electricalcontact with connectors 20B10 and brought into an assembly 20B30. One ormore lens elements 20B40 can be optically coupled to the light source.The lens design and properties can be selected so that the desireddirectional beam pattern for a lighting product is achieved for a givenLES. The directional lighting product may be an LED module, a retrofitlamp 20B70, or a lighting fixture 20C30. In the case of a retrofit lamp,an electronic driver can be provided with a surrounding member 20B60,the driver to condition electrical power from an external source torender it suitable for the LED light source. The driver can beintegrated into the retrofit lamp. In the case of a fixture, anelectronic driver is provided which conditions electrical power from anexternal source to make it suitable for the LED light source, with thedriver either integrated into the fixture or provided externally to thefixture. In the case of a module, an electronic driver can be providedto condition electrical power from an external source to render itsuitable for the LED light source, with the driver either integratedinto the module or provided externally to the module. Examples ofsuitable external power sources include mains AC (e.g., 120 Vrms AC or240 Vrms AC), low-voltage AC (e.g., 12 VAC), and low-voltage DC (e.g.,12 VDC). In the case of retrofit lamps, the entire lighting product maybe designed to fit standard form factors (e.g., ANSI form factors).Examples of retrofit lamp products include LED-based MR16, PAR16, PAR20,PAR30, PAR38, BR30, A19 and various other lamp types. Examples offixtures include replacements for halogen-based and ceramic metalhalide-based directional lighting fixtures.

In some embodiments, the present disclosure can be applied tonon-directional lighting applications. In these embodiments, one or morelight-emitting diodes (LEDs), as taught by the disclosure, can bemounted on a submount or package to provide an electricalinterconnection. The submount or package can be, for example, a ceramic,oxide, nitride, semiconductor, metal, or combination of any of theforegoing, that includes electrical interconnection capability for thevarious LEDs. The submount or package can be mounted to a heatsinkmember via a thermal interface. The LEDs can be configured to produce adesired emission spectrum, either by mixing primary emissions fromvarious LEDs, or by having the LEDs photo-excite wavelengthdown-conversion materials such as phosphors, semiconductors, orsemiconductor nanoparticles (“quantum dots”), or a combination thereof.The LEDs can be distributed to provide a desired shape of the lightsource. For example, one common shape is a linear light source forreplacement of conventional fluorescent linear tube lamps. One or moreoptical elements can be coupled to the LEDs to provide a desirednon-directional light distribution. The non-directional lighting productmay be an LED module, a retrofit lamp, or a lighting fixture. In thecase of a retrofit lamp, an electronic driver can be provided tocondition electrical power from an external source to render it suitablefor the LED light source, with the driver integrated into the retrofitlamp. In the case of a fixture, an electronic driver is provided tocondition electrical power from an external source to render it suitablefor the LED light source, with the driver either integrated into thefixture or provided externally to the fixture. In the case of a module,an electronic driver can be provided to condition electrical power froman external source to render it suitable for the LED light source, withthe driver either integrated into the module or provided externally tothe module. Examples of external power sources include mains AC (e.g.,120 Vrms AC or 240 Vrms AC), low-voltage AC (e.g., 12 VAC), andlow-voltage DC (e.g., 12 VDC). In the case of retrofit lamps, the entirelighting product may be designed to fit standard form factors (e.g.,ANSI form factors). Examples of retrofit lamp products include LED-basedreplacements for various linear, circular, or curved fluorescent lamps.An example of a non-directional lighting product is shown in FIG. 20C.Such a lighting fixture can include replacements for fluorescent-basedtroffer luminaires. In this embodiment, LEDs are mechanically securedinto a package 20C10, and multiple packages are arranged into a suitableshape such as linear array 20C20.

Some embodiments of the present disclosure can be applied tobacklighting for flat panel display applications. In these embodiments,one or more light-emitting diodes (LEDs), as taught by this disclosure,can be mounted on a submount or package to provide an electricalinterconnection. The submount or package can be a ceramic, oxide,nitride, semiconductor, metal, or combination of any of the foregoingthat include electrical interconnection capability for the various LEDs.The submount or package can be mounted to a heatsink member via athermal interface. The LEDs can be configured to produce a desiredemission spectrum, either by mixing primary emission from various LEDs,or by having the LEDs photo-excite wavelength down-conversion materialssuch as phosphors, semiconductors, or semiconductor nanoparticles(“quantum dots”), or a combination of any of the foregoing. The LEDs canbe distributed to provide a desired shape of the light source. Onecommon shape is a linear light source. The light source can be opticallycoupled to a lightguide for the backlight. This can be achieved bycoupling at the edge of the lightguide (edge-lit), or by coupling lightfrom behind the lightguide (direct-lit). The lightguide distributeslight uniformly toward a controllable display, such as a liquid crystaldisplay (LCD) panel. The display converts the LED light into desiredimages based on electrical control of light transmission and its color.One way to control the color is by use of filters (e.g., color filtersubstrate 20D40, filter substrate 20D40). Alternatively, multiple LEDsmay be used and driven in pulsed mode to sequence the desired primaryemission colors (e.g., using a red LED 20D30, a green LED 20D10, and ablue LED 20D20). Optional brightness-enhancing films may be included inthe backlight “stack”. The brightness-enhancing films narrow the flatpanel display emission to increase brightness at the expense of theobserver viewing angle. An electronic driver can be provided tocondition electrical power from an external source to render it suitablefor the LED light source for backlighting, including any colorsequencing or brightness variation per LED location (e.g.,one-dimensional or two-dimensional dimming). Examples of external powersources include mains AC (e.g., 120 Vrms AC or 240 Vrms AC), low-voltageAC (e.g., 12 VAC), and low-voltage DC (e.g., 12 VDC). Examples ofbacklighting products are shown in FIG. 20D1, FIG. 20D2, FIG. 20E1 andFIG. 20E2.

Some embodiments of the present disclosure can be applied to automotiveforward lighting applications, as shown in FIG. 20F. In theseembodiments, one or more light-emitting diodes (LEDs) can be mounted ona submount or on a rigid or semi-rigid package 20F10 to provide anelectrical interconnection. The submount or package can be a ceramic,oxide, nitride, semiconductor, metal, or combination thereof, thatinclude electrical interconnection capability for the various LEDs. Thesubmount or package can be mounted to a heatsink member via a thermalinterface. The LEDs can be configured to produce a desired emissionspectrum, either by mixing primary emission from various LEDs, or byhaving the LEDs photo-excite wavelength down-conversion materials suchas phosphors, semiconductors, or semiconductor nanoparticles (“quantumdots”), or a combination of any of the foregoing. The total lightemitting surface (LES) of the LEDs and any down-conversion materialsform a light source. One or more lens elements 20F20 can be opticallycoupled to the light source. The lens design and properties can beselected to produce a desired directional beam pattern for an automotiveforward lighting application 20F30 for a given LED. An electronic drivercan be provided to condition electrical power from an external source torender it suitable for the LED light source. Examples of external powersources for automotive applications include low-voltage DC (e.g., 12VDC). An LED light source may perform a high-beam function, a low-beamfunction, a side-beam function, or any combination thereof. An exampleof an automotive forward lighting product is shown in FIG. 20F.

In some embodiments, the present disclosure can be applied to digitalimaging applications, such as illumination for mobile-phone and digitalstill cameras. In these embodiments, one or more light-emitting diodes(LEDs), as taught by the disclosure, can be mounted on a submount orpackage to provide an electrical interconnection. The submount orpackage can be, for example, a ceramic, oxide, nitride, semiconductor,metal, or combination of any of the foregoing, that include electricalinterconnection capability for the various LEDs. The submount or packagecan be mounted to a circuit board member. The LEDs can be configured toproduce a desired emission spectrum, either by mixing primary emissionfrom various LEDs, or by having the LEDs photo-excite wavelengthdown-conversion materials such as phosphors, semiconductors, orsemiconductor nanoparticles (“quantum dots”), or a combination thereof.The total light emitting surface (LES) of the LEDs and anydown-conversion materials form a light source. One or more lens elementscan be optically coupled to the light source. The lens design andproperties can be selected so that the desired directional beam patternfor an imaging application is achieved for a given LES. An electronicdriver can be provided to condition electrical power from an externalsource to render it suitable for the LED light source. Examples ofsuitable external power sources for imaging applications includelow-voltage DC (e.g., 5 VDC). An LED light source may perform ahigh-beam function, low-beam function, side-beam function,daytime-running-light, or any combination thereof. An example of animaging lighting product is shown in FIG. 20G.

FIG. 20 is a diagram illustrating a smart phone architecture 20H00. Asshown, the smart phone 20H06 includes a housing, display, and interfacedevice, which may include a button, microphone, and/or touch screen. Incertain embodiments, a phone has a high resolution camera device, whichcan be used in various modes. An example of a smart phone can be aniPhone from Apple Inc. of Cupertino, Calif. Alternatively, a smart phonecan be a Galaxy from Samsung or others.

In an example, the smart phone may include one or more of the followingfeatures (which are found in an iPhone 4 from Apple Inc., although therecan be variations), see www.apple.com:

-   -   GSM model: UMTS/HSDPA/HSUPA (850, 900, 1900, 2100 MHz); GSM/EDGE        (850, 900, 1800, 1900 MHz)    -   CDMA model: CDMA EV-DO Rev. A (800, 1900 MHz)    -   802.11b/g/n Wi-Fi (802.11n 2.4 GHz only)    -   Bluetooth 2.1+EDR wireless technology    -   Assisted GPS    -   Digital compass    -   Wi-Fi    -   Cellular    -   Retina display    -   3.5-inch (diagonal) widescreen multi-touch display    -   800:1 contrast ratio (typical)    -   500 cd/m2 max brightness (typical)    -   Fingerprint-resistant oleophobic coating on front and back    -   Support for display of multiple languages and characters        simultaneously    -   5-megapixel iSight camera    -   Video recording, HD (720p) up to 30 frames per second with audio    -   VGA-quality photos and video at up to 30 frames per second with        the front camera    -   Tap to focus video or still images    -   LED flash    -   Photo and video geotagging    -   Built-in rechargeable lithium-ion battery    -   Charging via USB to computer system or power adapter    -   Talk time: Up to 7 hours on 3G, up to 14 hours on 2G (GSM)    -   Standby time: Up to 300 hours    -   Internet use: Up to 6 hours on 3G, up to 10 hours on Wi-Fi    -   Video playback: Up to 10 hours    -   Audio playback: Up to 40 hours    -   Frequency response: 20 Hz to 20,000 Hz    -   Audio formats supported: AAC (8 to 320 Kbps), protected AAC        (from iTunes Store), HE-AAC, MP3 (8 to 320 Kbps), MP3 VBR,        audible (formats 2, 3, 4, audible enhanced audio, AAX, and        AAX+), Apple lossless, AIFF, and WAV    -   User-configurable maximum volume limit    -   Video out support at up to 720p with Apple digital AV adapter or        Apple VGA adapter; 576p and 480p with Apple component AV cable;        576i and 480i with Apple composite AV cable (cables sold        separately)    -   Video formats supported: H.264 video up to 720p, 30 frames per        second, main profile Level 3.1 with AAC-LC audio up to 160 Kbps,        48 kHz, stereo audio in .m4v, .mp4, and .mov file formats;        MPEG-4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per        second, simple profile with AAC-LC audio up to 160 Kbps per        channel, 48 kHz, stereo audio in .m4v, .mp4, and .mov file        formats; motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels,        30 frames per second, audio in ulaw, PCM stereo audio in .avi        file format    -   Three-axis gyro    -   Accelerometer    -   Proximity sensor    -   Ambient light sensor

Embodiment of the present disclosure may be used with other electronicdevices. Examples of suitable electronic devices include a portableelectronic device, such as a media player, a cellular phone, a personaldata organizer, or the like. In such embodiments, a portable electronicdevice may include a combination of the functionalities of such devices.In addition, an electronic device may allow a user to connect to andcommunicate through the Internet or through other networks, such aslocal or wide area networks. For example, a portable electronic devicemay allow a user to access the internet and to communicate using e-mail,text messaging, instant messaging, or using other forms of electroniccommunication. By way of example, the electronic device may be similarto an iPod having a display screen or an iPhone available from AppleInc.

In certain embodiments, a device may be powered by one or morerechargeable and/or replaceable batteries. Such embodiments may behighly portable, allowing a user to carry the electronic device whiletraveling, working, exercising, and so forth. In this manner, anddepending on the functionalities provided by the electronic device, auser may listen to music, play games or video, record video or takepictures, place and receive telephone calls, communicate with others,control other devices (e.g., via remote control and/or Bluetoothfunctionality), and so forth while moving freely with the device. Inaddition, the device may be sized such that it fits relatively easilyinto a pocket or the hand of the user. While certain embodiments of thepresent disclosure are described with respect to portable electronicdevices, it should be noted that the presently disclosed techniques maybe applicable to a wide array of other, less portable, electronicdevices and systems that are configured to render graphical data, suchas a desktop computer.

FIG. 20I depicts an interconnection of components in an electronicdevice 20I00. Examples of electronic devices include an enclosure orhousing, a display, user input structures, and input/output connectorsin addition to the aforementioned interconnection of components. Theenclosure may be formed from plastic, metal, composite materials, orother suitable materials, or any combination thereof. The enclosure mayprotect the interior components of the electronic device from physicaldamage, and may also shield the interior components from electromagneticinterference (EMI).

The display may be a liquid crystal display (LCD), a light emittingdiode (LED) based display, an organic light emitting diode (OLED) baseddisplay, or some other suitable display. In accordance with certainembodiments of the present disclosure, the display may display a userinterface and various other images such as logos, avatars, photos, albumart, and the like. Additionally, in certain embodiments, a display mayinclude a touch screen through which a user may interact with the userinterface. The display may also include various functions and/or systemindicators to provide feedback to a user such as power status, callstatus, memory status, or the like. These indicators may be incorporatedinto the user interface displayed on the display.

In certain embodiments, one or more of the user input structures can beconfigured to control the device, such as by controlling a mode ofoperation, an output level, an output type, etc. For example, the userinput structures may include a button to turn the device on or off.Further, the user input structures may allow a user to interact with theuser interface on the display. Embodiments of the portable electronicdevice may include any number of user input structures, includingbuttons, switches, a control pad, a scroll wheel, or any other suitableinput structures. The user input structures may work with the userinterface displayed on the device to control functions of the deviceand/or any interfaces or devices connected to or used by the device. Forexample, the user input structures may allow a user to navigate adisplayed user interface or to return such a displayed user interface toa default or home screen.

Certain device may also include various input and output ports to allowconnection of additional devices. For example, a port may be a headphonejack that provides for the connection of headphones. Additionally, aport may have both input and output capabilities to provide forconnection of a headset (e.g., a headphone and microphone combination).Embodiments of the present disclosure may include any number of inputand/or output ports, such as headphone and headset jacks, universalserial bus (USB) ports, IEEE-1394 ports, and AC and/or DC powerconnectors. Further, a device may use the input and output ports toconnect to and send or receive data with any other device, such as otherportable electronic devices, personal computers, printers, or the like.For example, in one embodiment, the device may connect to a personalcomputer via an IEEE-1394 connection to send and receive data files suchas media files. Further details of the device can be found in U.S. Pat.No. 8,294,730.

FIG. 20H is a system diagram with a smart phone according to anembodiment of the present disclosure. A server 20H02 is in electroniccommunication with a handheld electronic device 20H06 having functionalcomponents such as a processor 20H08, memory 20H10, graphics accelerator20H12, accelerometer 20H14, communications interface 20H11, compass20H18, GPS 20H20, display 20H22, and an input device 20H24. Each deviceis not limited to the illustrated components. The components may behardware, software or a combination of both.

In some examples, instructions can be input to the handheld electronicdevice 20H06 through an input device 20H24 that instructs the processor20H08 to execute functions in an electronic imaging application. Onepotential instruction can be to generate a wireframe of a captured imageof a portion of a human user. In that case the processor 20H08 instructsthe communications interface 20H11 to communicate with the server 20H02and transfer a human wireframe or image data. The data is transferred bythe communications interface 20H11 and either processed by the processor20H08 immediately after image capture or stored in memory 20H10 forlater use, or both. The processor 20H08 also receives informationregarding the display's 20H22 attributes, and can calculate theorientation of the device, e.g., using information from an accelerometer20H14 and/or other external data such as compass headings from a compass20H18, or GPS location from a GPS chip 20H20, and the processor thenuses the information to determine an orientation in which to display theimage depending upon the example.

The captured image can be drawn by the processor 20H08, by a graphicsaccelerator 20H12, or by a combination of the two. In some embodiments,the processor can be the graphics accelerator 20H12. The image can firstbe drawn in memory 20H10 or, if available, the memory directlyassociated with the graphics accelerator 20H12. The methods describedherein can be implemented by the processor 20H08, the graphicsaccelerator 20H12, or a combination of the two to create the image andrelated wireframe. Once the image or wireframe is drawn in memory, itcan be displayed on the display 20H22.

FIG. 20I is a diagram of a smart phone system diagram according to anembodiment of the present disclosure. Computer system 20I00 is anexample of computer hardware, software, and firmware that can be used toimplement the disclosures above. System 20I00 includes a processor20I26, which is representative of any number of physically and/orlogically distinct resources capable of executing software, firmware,and hardware configured to perform identified computations. Processor20I26 communicates with a chipset 20I28 that can control input to andoutput from processor 20I26. In this example, chipset 20I28 outputsinformation to display 20I42 and can read and write information tonon-volatile storage 20I44, which can include magnetic media and solidstate media, for example. Chipset 20I28 also can read data from andwrite data to RAM 20I46. A bridge 20I32 for interfacing with a varietyof user interface components can be provided for interfacing withchipset 20I28. Such user interface components can include a keyboard20I34, a microphone 20I36, touch-detection-and-processing circuitry20I38, a pointing device such as a mouse 20I40, and so on. In general,inputs to system 20I00 can come from any of a variety ofmachine-generated and/or human-generated sources.

Chipset 20I28 also can interface with one or more data networkinterfaces 20I30 that can have different physical interfaces. Such datanetwork interfaces 20I30 can include interfaces for wired and wirelesslocal area networks, for broadband wireless networks, as well aspersonal area networks. Some applications of the methods for generatingand displaying and using the GUI disclosed herein can include receivingdata over a physical interface 20I31 or be generated by the machineitself by a processor 20I26 analyzing data stored in memory 20I10 or20I46. Further, the machine can receive inputs from a user via a deviceskeyboard 20I34, microphone 20I36, touch device 20I38, and pointingdevice 20I40 and execute appropriate functions, such as browsingfunctions by interpreting these inputs using processor 20I26.

In embodiments where the invention is used in a display system, specificcolor properties of the emitted light may be desirable. For example, itmay be desirable that the emitted light have a large color gamut. Oneknown way to measure color gamut in display applications is by acomparison to the NTSC gamut. In some embodiments, the gamut is 50%,70%, 90% or 100% of the NTSC gamut. In some embodiments, the gamut isless than 50%, less than 70%, less than 90%, and in some embodiments,less than 100% of the NTSC gamut.

Finally, it should be noted that there are alternative ways ofimplementing the embodiments disclosed herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive,and the claims are not to be limited to the details given herein, butmay be modified within the scope and equivalents thereof.

What is claimed is:
 1. A light emitting diode (LED) device comprising: asubmount; at least one pump LED, grown on a substrate, wherein the LEDcomprises a light-emitting active region comprising a base area; acolor-converting material overlying the at least one pump light-emittingdiode; and at least one flat emitting surface having an emitting areaand emitting substantially white light; wherein the area of the at leastone flat emitting surface is characterized by an area less than 250μm×250 μm, and a surface brightness of 800 mW/mm² or more; wherein theLED device is characterized by a wall-plug efficiency of at least 25%.2. The LED device of claim 1, wherein the substrate comprises a bulkIII-nitride-containing compound.
 3. The LED device of claim 1, whereinthe at least one pump LED is configured to emit violet light.
 4. The LEDdevice of claim 1, wherein the at least one pump LED is configured toemit blue light.
 5. The LED device of claim 1, wherein the at least oneflat emitting surface emits light characterized by a CCT in a range fromabout 2000K to about 10000K.
 6. The LED device of claim 1, wherein theat least one LED is configured to be driven at a current density in arange of about 100 A/cm² to about 1000 A/cm².
 7. The LED device of claim1, wherein light emitted by the LED device exhibits a gamut of at least70% of NTSC gamut.
 8. The LED device of claim 1, wherein the at leastone LED comprises a flip-chip configuration.
 9. The LED device of claim1, wherein the base area is characterized by a base shape that issubstantially rectilinear.
 10. The LED device of claim 1, wherein thesubmount is characterized by a reflectivity higher than 80% within atleast a wavelength in a range of 400 nm to 700 nm.
 11. The LED device ofclaim 1, further comprising at least one reflective material inproximity to at least one of the at least one LED and in proximity tothe color conversion material.
 12. The LED device of claim 11, whereinthe reflective material is characterized by a reflectivity higher than90% within at least a wavelength in a range of 400 nm to 700 nm.
 13. TheLED device of claim 11, comprising an air gap between the reflectivematerial and at least one of the at least one LED and the colorconversion material.
 14. The LED device of claim 13, wherein at leastone of the reflective material or the submount forms a diffusereflector.
 15. The LED device of claim 14, wherein at least one of thereflective material or the submount comprises a metal material.
 16. TheLED device of claim 14, wherein at least one of the reflective materialor the submount comprises a dielectric stack.
 17. The LED device ofclaim 1, wherein a combined thickness of the submount, the at least oneLED, and the light-converting material is less than 1 mm.
 18. A lightemitting diode (LED) device comprising a LED, wherein the LED comprises:a base area less than 250 μm×250 μm; and an emitting surface comprisingan emitting area configured to emit substantially white light; whereinthe emitting surface is characterized by a surface brightness of 800mW/mm² or more; and wherein at least 80% of the base area is used forlight generation.
 19. A light emitting diode (LED) device comprising: atleast one pump LED, wherein the at least one pump LED comprises: a basearea; a color-converting material overlying the at least one pump LED;and at least one emitting surface configured to emit substantially whitelight, wherein, the at least one emitting surface has an area less than250 μm×250 μm; is characterized by a surface brightness of 800 mW/mm² ormore; and the at least one pump LED is characterized by a wall-plugefficiency of at least 25%; and a display component wherein the at leastone pump light-emitting diode is coupled to the display component. 20.The LED device of claim 19, wherein the display component comprises aflat panel display.